Pixel Coordinates of Rendered Image with Python
It seems I found the way how to get pixel coordinates through Rendering Crop. Select a Crop Node and use the script.



import bpy

scene = bpy.context.scene
nodes = scene.node_tree.nodes
cropNode = nodes.active

if cropNode.type == 'CROP':
    nodes.active.min_x = scene.render.border_min_x * scene.render.resolution_x
    nodes.active.max_x = scene.render.border_max_x * scene.render.resolution_x
    nodes.active.min_y = scene.render.border_min_y * scene.render.resolution_y
    nodes.active.max_y = scene.render.border_max_y * scene.render.resolution_y